Process and apparatus for building pneumatic tyres

ABSTRACT

During building of a tyre, at least one component of elastomeric material is manufactured through application of an elongated element in the form of coils disposed side by side and/or superposed onto a forming support driven in rotation and transversely moved in front of an applicator device. The elongated element is formed by feeding a continuous thread element coming from an extruder between two shaping rollers. During formation, a detector operating close to the shaping rollers cyclically detects the width of the elongated element and the cross-section area of the continuous thread element to monitor the volumetric flow rate of the continuous thread element close to the shaping rollers. The feeding speed of the continuous thread element toward the shaping rollers is adjusted through feedback on the extruder or on a driving device operating downstream of the extruder itself, to keep the volumetric flow rate value within a predetermined range.

The present invention relates to a process for building pneumatic tyres,and to an apparatus for building pneumatic tyres based on said process.

A tyre generally comprises a carcass structure including at least onecarcass ply having end flaps in engagement with respective annularanchoring structures, each usually made up of at least one substantiallycircumferential annular insert to which at least one filling inserttapering radially away from the rotation axis is applied.

A belt structure comprising one or more belt layers is associated withthe carcass structure at a radially external position, said belt layersbeing disposed in radial superposed relationship with respect to eachother and to the carcass ply and having textile or metallic reinforcingcords with a crossed orientation and/or substantially parallel to thecircumferential extension direction of the tyre.

A tread band is applied to the belt structure at a radially externalposition, which tread band is also made of elastomeric material likeother semi-finished products constituting the tyre.

A so-called “under-layer” of elastomeric material having propertiesadapted to ensure steady fastening of the tread band itself, can beinterposed between the tread band and the belt structure.

Respective sidewalls of elastomeric material are also applied to theside surfaces of the carcass structure, each extending from one of theside edges of the tread band until close to the respective annularanchoring structure to the beads.

It is to be pointed out, to the aims of the present description, that bythe term “elastomeric material” it is intended a compound comprising atleast one elastomeric polymer and at least one reinforcing filler.Preferably, this compound further comprises additives such as across-linking agent and/or a plasticizer, for example. Due to thepresence of the cross-linking agent, this material can be cross-linkedthrough heating, so as to form the final manufactured product.

In tyres of the tubeless type, the carcass ply is internally coated witha so-called liner consisting of a layer of preferably butyl-basedelastomeric material having optimal air-tightness features and extendingfrom one side of the beads to the other.

In tyres of the run flat type or for other particular uses, the carcassstructure can be further provided with auxiliary support inserts ofelastomeric material, placed at an axially internal position relative toeach of the sidewalls. These auxiliary support inserts usually referredto as “sidewall inserts” lend themselves to support the loadstransmitted to the wheel in case of accidental deflation of the tyre toenable the vehicle to run on, under safety conditions.

In many known processes for manufacture of a tyre, the carcass structureand belt structure, as well as the tread band, sidewalls and any otherelastomeric structural element, are made separately from each other inrespective work stations, and then stowed in storage stations orwarehouses from which they are subsequently picked up for mutualassembly along a tyre building line.

It is to be pointed out that in this context by “component ofelastomeric material” of the tyre it is intended any part of elastomericmaterial of the tyre (tread band, sidewalls, liner, under-liner, fillersin the bead region, inserts at the sidewalls in run flat tyres,abrasion-preventing inserts, for example), or a portion thereof, or yetthe assembly formed of two or more of said parts or portions thereof.

More recently also production processes have been developed in which, asdescribed in WO 00/35666 for example in the name of the same Applicant,components of elastomeric material of the tyre are obtained throughdelivery of an elastomeric elongated element from an extruder, forsuitable distribution of same on a toroidal support carrying the tyrebeing processed, while rotation of said tyre around its axis is beingcaused. Simultaneously, the toroidal support hanging from a robotizedarm, is moved in front of the extruder to cause transverse distributionof the elongated element and thus form a plurality of circumferentialcoils therewith, which coils are disposed in axial side by siderelationship and/or radial superposition and the orientation andmutual-superposition parameters of which are adjusted so as to controlthe thickness variations to be given to the component of elastomericmaterial during manufacture, based on a predetermined deposition schemepreviously set on an electronic computer.

In U.S. Pat. No. 5,171,394, components of elastomeric material of a tyreare formed on a rigid drum by means of a positive-displacement extruderhaving an outlet port of small sizes placed close to the surface towhich the elastomer is to be applied. The components of elastomericmaterial are formed by actuation of the extruder relative to the surfaceof the toroidal support driven in rotation, concurrently with deliveryof the elastomeric material in the form of a continuous elongatedelement.

U.S. Pat. No. 6,955,734 discloses obtaining components of elastomericmaterial of a tyre by laying an elastomeric elongated element on aforming support, said elongated element being delivered by a systemcomprising a screw extrusion unit terminating at a gear pump, downstreamof which an extrusion head having a delivery nozzle is arranged.Disposed between the delivery nozzle and the forming support is a pairof guide rollers the outer cylindrical surfaces of which are mutuallyspaced apart to define a gauged passage; thus the elongated element isgauged as to its thickness during passage through the clearance definedbetween the rollers, and also guided and applied against the formingsupport by one of the guide rollers, elastically urged against theforming support itself.

The Applicant has verified that the tyres obtained by the abovedescribed building methods can have geometric and structural faultsbringing about adverse effects both in terms of production waste and asregards the product quality. In particular, in spite of the attentionand expedients adopted during manufacture of the individual componentsof elastomeric material through spiralling operations, the geometric andsize accuracy of same often appears to be unsatisfactory. This problemis particularly apparent with reference to those components ofelastomeric material that, after building of the tyre, must be submittedto a moulding operation of the so-called “imposed-volume” type, in whichthe tyre or given parts of same, the beads for example, are enclosed ina moulding cavity substantially having the same volume as that taken upby the material constituting the part itself submitted to moulding. Infact it has been verified that under this circumstance, small amounts ofexcess material in the component of elastomeric material submitted tomoulding can prevent a correct closure of the mould and allow migrationof the elastomeric material towards different tyre regions (in aradially external direction for example in the case of the beads), whilematerial lacks of small amounts give rise to clear geometric andstructural faults on the finished product.

The Applicant has also noticed that accuracy in working the componentsof elastomeric material is affected by different concurrent factors inthe extrusion process, such as oscillations in the temperature andviscosity values of the elastomeric material within the strainer, wearof the inner members of the extrusion apparatus, pressure variationswithin the extrusion apparatus during the starting and stopping steps,and yet other factors that can hardly vary in a predictable andcontrollable manner.

In accordance with the Applicant's perception, all these variables causeas the final effect, more or less sudden important variations in thecross-section sizes of the elongated element applied to the formingsupport.

In accordance with the present invention, the Applicant has found thepossibility of overcoming the above described problems by providing apair of counter-rotating shaping rollers disposed downstream of thestrainer for carrying out shaping of a continuous elongated element, andby executing during working, a constant control of the volumetric flowrate of the material passing between the shaping rollers, to modify thelinear feeding speed of the material to the rollers in response topossible flow rate variations, so as to keep the elongated-elementsection variations within a predetermined range.

In more detail, in a first aspect the present invention relates to aprocess for building tyres, comprising the step of assembling componentsof elastomeric material on a forming support, in which at least one ofsaid components of elastomeric material is manufactured by the steps of:

-   -   delivering a continuous thread element of elastomeric material        from an extruder;    -   shaping the continuous thread element coming from the extruder,        to form an elongated element of a predetermined cross-section        outline;    -   applying the elongated element in the form of wound up coils        onto the forming support, to form said at least one component of        elastomeric material of the tyre;        wherein said shaping operation is carried out by feeding the        continuous thread element through a pair of counter-rotating        shaping rollers;        said process further comprising the steps of:    -   monitoring at least one parameter indicative of the volumetric        flow rate of the continuous thread element close to the shaping        rollers;    -   adjusting a feeding speed of the continuous thread element        towards the shaping rollers to keep the volumetric flow rate        value within a predetermined range.

In accordance with a second aspect of the present invention it isproposed an apparatus for building tyres comprising:

-   -   at least one forming support;    -   at least one assembly device to assemble components of        elastomeric material on the forming support;        wherein said at least one assembly device comprises:    -   at least one extruder to deliver a continuous thread element of        elastomeric material;    -   at least one shaping device to shape the continuous thread        element coming from the extruder and comprising at least one        pair of counter-rotating shaping rollers engaging the continuous        thread element to form an elongated element having a        predetermined cross-section outline;    -   at least one applicator device to apply said elongated element        wound up into coils onto the forming support, to form said at        least one component of elastomeric material of the tyre;        wherein said at least one shaping device further comprises:    -   at least one device for monitoring at least one parameter        indicative of the volumetric flow rate of the continuous thread        element close to the shaping rollers;    -   at least one adjusting device to adjust a feeding speed of the        continuous thread element towards the shaping rollers to keep        the volumetric flow rate value within a predetermined range.

When the monitoring device detects a flow rate that is lower than apredetermined minimum threshold, an increase in the feeding speed of thecontinuous thread element is carried out, said feeding speed beingreduced when a flow rate higher than a pre-set maximum threshold isdetected. Thus a careful control of the quantity of elastomeric materialapplied to the forming support is obtained. Consequently, a greatergeometric and size accuracy of the individual components of elastomericmaterial of the tyre formed by deposition of the elongated element canbe obtained.

Use of counter-rotating rollers to carry out forming of the elongatedelement further allows a continuous thread element of circular orapproximately circular section to be extruded. Thus a more fluent anddirect outflow of the elastomeric material can be provided from theoutlet port of the extruder thus restricting the stresses usuallyimposed to the elastomeric material in the extruder's exit die that inthe known art has important section variations to cause shaping of theelongated element in its final conformation. Thus all problems connectedwith wear of the surfaces of the dies used in the known art areeliminated as well as the drawbacks concerned with formation of depositsand incrustations within the die itself. It is also possible to reducethe temperature of the elastomeric material within the die, so thatoverheating and/or cross-linking initiation in the stopping steps of thelaying operation does not occur.

Feeding of the elastomeric material to the shaping rollers can becarried out directly by the extruder, or by a pair of rollers or otherdriving devices operating downstream of the extruder itself. In thiscase, a storage step of the elastomeric thread element can beadvantageously carried out at a storage length included between theextruder and the shaping rollers, so as to enable greater cooling andsize stabilisation of the continuous thread element before it isdisposed between the shaping rollers.

Shaping is preferably carried out by conducting the continuous threadelement through a shaped clearance defined between the shaping rollersand preferably engaging said continuous thread element substantially onthe whole cross-section outline extension of same, so as to give theformed elongated element a desired cross-section outline, preferably oftrapezoidal form.

In a preferred embodiment, the flow rate of the elastomeric materialbetween the shaping rollers is monitored by cyclically detecting thecross-section area of the continuous thread element immediately upstreamof the shaped clearance, or the width of the elongated elementimmediately downstream of the shaped clearance. In the last-mentionedcase, during shaping, at least one side edge of variable size dependingon the flow rate of the elastomeric material between the shaping rollerscan be advantageously formed on the elongated element, so as to increaseaccuracy and reading sensitivity of the elongated element width.

The feeding speed of the thread element towards the shaping rollers canbe advantageously adjusted by modifying the delivery speed of theelastomeric material through the extruder, by intervening on therotation of a feeding screw being part of said extruder and/or of apositive-displacement pump, of the gear type for example, possiblydisposed upstream of an outlet port of the extruder.

Alternatively, the feeding speed of the thread element towards theshaping rollers is adjusted by acting on a driving device downstream ofthe extruder.

Preferably, application of the elongated element onto the formingsupport takes place by at least one roller or other applicator membersoperatively supported with respect to the shaping rollers and acting inthrust relationship towards the forming support. This applicator rollercan advantageously be spaced from the shaping rollers, so that thelatter do not hinder movement of the applicator roller on the surface ofthe forming support.

Further features and advantages will become more apparent from thedescription of a preferred, but not exclusive, embodiment of a processand an apparatus for building tyres, in accordance with the presentinvention. This description will be set out hereinafter with referenceto the accompanying drawings, given by way of non-limiting example, inwhich:

FIG. 1 is a diagrammatic top view of a plant for producing tyrescomprising a building apparatus in accordance with the presentinvention;

FIG. 2 diagrammatically shows a detail of the plant in FIG. 1 from top;

FIG. 3 is a diagrammatic side view of an assembly device being part ofthe apparatus in reference, according to a first embodiment;

FIG. 4 is a diagrammatic side view of a second embodiment of theassembly device shown in FIG. 3;

FIG. 5 shows a section taken along line V-V in FIGS. 3 and 4, to anenlarged scale;

FIG. 6 is a diametrical section view of an example of a tyre obtainablein accordance with the present invention.

With reference to the drawings, a plant for producing tyres comprising abuilding apparatus 2 according to the present invention has beengenerally identified with reference numeral 1.

Plant 1 is intended for manufacture of tyres 3 (FIG. 6) essentiallycomprising at least one carcass ply 4 preferably internally coated witha so-called liner 5 or layer of elastomeric material impervious to air,two so-called “beads” 6 integrating respective annular anchoringstructures 7 possibly associated with elastomeric fillers 7 a and inengagement with the circumferential edges of the carcass ply 4, a beltstructure 8 circumferentially applied around the carcass ply 4, a treadband 9 circumferentially superposed on the belt structure 8, at aso-called crown region of tyre 3, and two sidewalls 10 applied to thecarcass ply 4 at laterally opposite positions, each at a side region ofthe tyre 3, extending from the corresponding bead 6 to the correspondingside edge of the tread band 9.

In run flat tyres or tyres intended for particular uses, auxiliarysupport inserts (not shown) can be further provided, of the type usuallyreferred to as “sidewall inserts” for example, applied close to thesidewalls internally of the carcass ply 4 or between two paired carcassplies 4, and/or at an axially external position to said at least onecarcass ply 4.

The building apparatus 2 may comprise a plurality of building stations11, 12, 13, 14, 15, each being for example provided to form onecomponent of the tyre 3 being processed directly on a forming support 16preferably of toroidal conformation, having a forming surface 16 a witha conformation corresponding to the inner conformation of the tyre 3itself when building has been completed. Alternatively, one or morecomponents of the tyre 3 being processed, instead of being directlymanufactured on the forming support 16 of toroidal conformation, areprovided to be obtained as semifinished products from preceding workingsteps and to be assembled to other components on a forming drum that canhave a cylindrical conformation or other shape different from that ofthe forming support 16 described above.

By way of example, shown in FIG. 1 is a first station 11 at which liner5 is manufactured through winding of a continuous elongated element ofelastomeric material into coils disposed in mutual side by siderelationship and distributed along the forming surface 16 a of theforming support 16 of toroidal conformation. In at least one secondbuilding station 12, manufacture of one or more carcass plies 4 can becarried out, which carcass plies are obtained by laying on the formingsupport 16, in circumferentially approached relationship, strip-likeelements obtained from a continuous strip of elastomeric materialcomprising textile or metallic cords disposed in parallel side by siderelationship. A third building station 13 can be dedicated tomanufacture of the annular anchoring structures 7 integrated into thebeads 6 of tyre 3, through lying of at least one continuous threadelement in the form of radially superposed coils and comprising at leastone rubberised metallic cord. At least one fourth building station 14can be dedicated to manufacture of the annular belt structure 8,obtained by laying, in circumferentially approached relationship,strip-like elements obtained from a continuous strip of elastomericmaterial comprising preferably metallic cords mutually parallel, and/orby winding at least one rubberised preferably metallic reinforcing cordinto axially approached coils, in the crown portion of tyre 3. At leastone fifth building station 15 can be provided for manufacture of thetread band 9 and sidewalls 10. The tread band 9 and sidewalls 10 arepreferably obtained through winding of at least one continuous elongatedelement of elastomeric material into mutually approached coils.

The building stations 11, 12, 13, 14, 15 can operate simultaneously,each on a respective tyre 3 being processed, carried by a respectiveforming support 16, sequentially transferred from a building station tothe subsequent building station, via robotized arms 17 or other suitabledevices.

Tyres 3 built by apparatus 2 are sequentially transferred to at leastone vulcanisation unit 18 integrated into the plant 1.

In accordance with the present invention, at least one of the componentsof elastomeric material of tyre 3, such as liner 5, fillers 7 a and/orother parts of elastomeric material of the beads 6, sidewalls 10, treadband 9, under-belt layer, tread band under-layer, abrasion-preventinginserts and/or others, is obtained by an assembly device generallydenoted at 19.

The assembly device 19 comprises at least one extruder 20 provided witha cylinder 21 into which elastomeric material is introduced. Thecylinder 21, heated to a controlled temperature included, just as anindication, between about 50° C. and about 100° C., operatively houses arotating screw 22, by effect of which the elastomeric material is urgedalong the cylinder 21 itself, towards an outlet port 23 of the extruder20. If required, the elastomeric material can be conveyed through apositive-displacement pump 24, a gear pump for example, that isoperatively interposed between the rotating screw 22 and the outlet port23, to ensure more uniformity of the flow rate therethrough.

Consequently, a continuous thread element 25 of raw elastomeric materialhaving a substantially circular cross-section outline is deliveredthrough the outlet port 23. Alternatively, the conformation of theoutlet port 23 and, as a result, of the cross-section outline of thecontinuous thread element 25, can be of the ellipsoid type. In both saidcases, the cross-section area of the outlet port 23 is preferablyincluded between about 10 mm² and about 200 mm².

Said size features enable the continuous thread element 25 to bedelivered at the desired linear speed corresponding to a so-called“target value” of the volumetric flow rate, included just as anindication between about 1 cm³/s and about 70 cm³/s, without too manydeformations being imposed to the mass of the elastomeric material closeto the outlet port 23. Thus it is advantageously possible to keep theelastomeric material temperature at the outlet port 23 to relativelyreduced values, included between about 80° C. and about 110° C., by wayof example.

The continuous thread element 25 coming from the extruder 20 is guidedtowards a shaping device 26 comprising at least one pair ofcounter-rotating shaping rollers 27. A first shaping roller 27 a can beof substantially cylindrical conformation, while at least one secondshaping roller 27 b has at least one circumferential groove 28 ofsuitable conformation. Thus a shaped clearance 29 is defined between themutually approached shaping rollers 27, which shaped clearance 29, in alying plane containing the rotation axes of the rollers themselves hasan area preferably included between about 50% and about 100% of the areaof the outlet port 23 of the extruder 20.

The continuous thread element 25 fed via the shaping rollers 27 is suchshaped that it forms an elongated element 30 having a predeterminedcross-section outline corresponding to the conformation of the shapedclearance. As clearly shown in FIG. 5, the shaped clearance 29preferably has a substantially trapezoidal outline, and engages theelongated element 30 substantially over the whole extension of thecross-section outline of same. In more detail, engagement between theshaped clearance 29 and elongated element 30 takes place at a first anda second respectively opposite base sides 30 a, 30 b, and a first and asecond height sides 30 c, 30 d, each extending between said first andsecond base sides 30 a, 30 b.

Operating close to the shaping rollers 27 is at least one device 31 formonitoring at least one parameter indicating the volumetric flow rate ofthe continuous thread element 25. The monitoring device 31 interactswith at least one adjusting device 32 to adjust the volumetric flow ratefor feeding the continuous thread element 25 towards the shaping rollers27.

The monitoring device 31, for instance, may comprise an ultrasonicdetector 33 of the laser beam or other type, positioned immediatelyupstream of the shaping rollers 27 (FIG. 4) and operating on thecontinuous thread element 25 to cyclically detect the cross-section areaof same at a frequency included between about 1 Hz and about 50 Hz, justas an indication.

In accordance with a further preferred solution, shown in FIG. 3, themonitoring device 31 comprises at least one laser beam, ultrasonic orother detector operating on one of the shaping rollers 27, preferablythe first roller 27 a of cylindrical conformation, downstream of theshaped clearance 29 to cyclically detect, at a frequency includedbetween about 1 Hz and about 50 Hz, the width size “D” of the elongatedelement 30 coming out of the shaped clearance itself.

The width-reading sensibility of detector 33 can be increased byproviding at least one lateral interspace 35 in the outline of theshaped clearance 29. In the example shown, two lateral interspaces 35are provided which extend on respectively opposite sides in theextension of the major base side 30 a of the trapezoidal outline of theclearance itself, preferably in order to give the shaped clearance 29 amaximum width “A” at least as large as a maximum acceptability value “B”for the elongated element width 30.

The presence of the lateral interspaces 35 causes formation of twotab-shaped projections 36 during shaping of the continuous threadelement 25, in the extension of the major base 30 a of the elongatedelement 30, which projections 36 have a thickness “S” included, by wayof example, between about 0.1 mm and about 0.5 mm. Due to the relativelyreduced thickness, the tab-shaped projections 36 show a noticeablyvariable width depending on variations, even if of small value, in theflow rate of the elastomeric material through the shaped clearance 29.In fact, due to the trapezoidal conformation of the shaped clearance 29,the elastomeric material acceding to the clearance itself tends to fillthe portion close to the minor base of the trapezoidal conformation andto subsequently expand into the region of the major base. A residualpart of the elastomeric material will therefore fill the lateralinterspaces 35 to a more or less important degree depending on the flowrate through the shaped clearance 29. As a result, even small variationsin the flow rate give rise to important size variations in thetab-shaped projections 36 formed along the edges of the elongatedelement 30 and, consequently, in the width “D” of the elongated element30 itself at a given instant. The linear speed of the continuous threadelement 25 being known, as it is detectable in case of need by anencoder (not shown) associated with a driving motor of the shapingrollers 27 for example, an electronic processing unit 34 being part ofthe adjusting device 32 can easily calculate the corresponding flow rateat each reading cycle carried out by detector 33.

A comparator 34 a associated with the electronic processing unit 34compares the flow rate parameters cyclically detected by detector 33with an ideal flow rate value stored beforehand, in order to enable theadjusting device 32 to adjust the feeding speed of the continuous threadelement 25 towards the shaping rollers 27 so that the volumetric flowrate through the shaped clearance 29 and the outlet port 23 shall bemaintained substantially equal to said predetermined target value, witha difference preferably less than 0.5%.

In more detail, when detector 33 detects a width of the elongatedelement corresponding to, or smaller than a predetermined minimumacceptability value “C”, the adjusting device 32 enables an increase inthe feeding speed of the continuous thread element 25 towards theshaping rollers 27. Vice versa, when detector 33 detects a width of theelongated element corresponding to or greater than a predeterminedmaximum acceptability value “B”, the adjusting device 32 enables areduction in the feeding speed of the continuous thread element 25towards the shaping rollers 27. The width “D” of the elongated elementis therefore maintained within said minimum and maximum acceptabilityvalues.

Adjustment of the feeding speed of the thread element can be carried outby modifying the delivery speed of the elastomeric material through theextruder 20, acting for instance on the rotation speed of the rotatingscrew 22 or, in the presence of the positive-displacement pump 24,modifying the driving speed of the pump itself.

In an alternative embodiment, as shown in the dashed box in FIG. 3, atleast one storage device 37 for accumulation of the continuous threadelement 25 can be interposed between the extruder 20 and the shapingrollers 27 to enable operation of the extruder 20 to be temporarilyincreased, slowed down or stopped without operation of the shapingrollers 27 being required to be correspondingly increased, slowed downor stopped, and vice versa. To this aim, the continuous thread element25 coming out of the extruder 20 is conveyed to a loop-shaped storagelength 38 extending from one intermediate roller 39 placed close to theoutlet port 23 of the extruder 20 for example, until a driving device 40consisting of opposite rollers for example, placed downstream of thestorage length 38 for feeding the shaping rollers 27 with the continuousthread element 25. In this case, the adjusting device 32 interacts withthe driving device 40 to adjust the feeding speed of the continuousthread element 25 towards the shaping rollers 27. An optical reader 41acting on the bottom of the storage length 38 operates a feedback on therotating screw 22 or the positive-displacement pump 24 if present, toadjust operation of the extruder 20 so as to keep the longitudinal sizeof the storage length 38 within a predetermined range.

An applicator device 42 operating downstream of the shaping rollers 27applies the elongated element 30 coming from the shaping rollers 27 ontothe forming support 16. During application, the forming support 16carried in overhanging by one of said robotized arms 17, is driven inrotation and suitably moved in front of the applicator device 42 todistribute the elongated element 30 in the form of coils disposed inside by side relationship and/or superposed, so as to form a liner 5 forexample, or any other component of elastomeric material of the tyre 3being processed.

The applicator device 42 comprises at least one roller or otherapplicator member 43 operatively supported relative to the shapingrollers 27, to some distance therefrom, and acting in thrustrelationship towards the forming support 16, by effect of a pneumaticactuator 44 for example, to apply the elongated element onto the formingsupport 16 itself.

1-45. (canceled)
 46. A process for building tyres, comprising the stepof assembling components of elastomeric material on a forming support,in which at least one of said components of elastomeric material ismanufactured by the steps of: delivering a continuous thread element ofelastomeric material from an extruder; shaping the continuous threadelement coming from the extruder, to form an elongated element of apredetermined cross-section outline; and applying the elongated elementin the form of wound up coils onto the forming support, to form said atleast one component of elastomeric material of the tyre, wherein saidshaping operation is carried out by feeding the continuous threadelement through a pair or counter-rotating shaping rollers; said processfurther comprising the steps of: monitoring at least one parameterindicative of volumetric flow rate of the continuous thread elementclose to the shaping rollers; and adjusting a feeding speed of thecontinuous thread element toward the shaping rollers to keep thevolumetric flow rate value within a predetermined range.
 47. The processas claimed in claim 46, wherein the delivery step is carried out byintroducing the elastomeric material into a cylinder longitudinallyhousing a rotating screw to urge the elastomeric material along thecylinder toward an outlet port of the extruder.
 48. The process asclaimed in claim 47, wherein the delivery step further comprises thestep of conveying the elastomeric material through a positivedisplacement pump operatively interposed between the rotating screw andthe outlet port of the extruder.
 49. The process as claimed in claim 46,further comprising a step of storing of continuous thread element foraccumulation of the continuous thread element in a storage lengthbetween the extruder and the shaping rollers.
 50. The process as claimedin claim 49, wherein the continuous thread element is fed to the shapingrollers by at least one driving device disposed downstream of thestorage length.
 51. The process as claimed in claim 46, wherein theparameter indicative of the volumetric flow rate comprises across-section area of the continuous thread element.
 52. The process asclaimed in claim 46, wherein the parameter indicative of the volumetricflow rate comprises a width size of the elongated element.
 53. Theprocess as claimed in claim 46, wherein the feeding speed of thecontinuous thread element toward the shaping rollers is adjusted bymodifying a delivery speed of the elastomeric material through theextruder.
 54. The process as claimed in claim 53, wherein the feedingspeed of the continuous thread element toward the shaping rollers isadjusted by modifying a rotation speed of a rotating screw, saidrotating screw being a part of said extruder.
 55. The process as claimedin claim 53, wherein the feeding speed of the continuous thread elementtoward the shaping rollers is adjusted by modifying a driving speed of apositive-volume pump operatively disposed upstream of an outlet port ofthe extruder.
 56. The process as claimed in claim 50, wherein thefeeding speed of the continuous thread element toward the shapingrollers is adjusted by acting on said at least one driving device. 57.The process as claimed in claim 46, wherein the shaping operationcomprises the step of conducting the continuous thread element through ashaped clearance defined between the shaping rollers.
 58. The process asclaimed in claim 57, wherein said shaped clearance engages the elongatedelement substantially over a whole extension of a cross-section outlineof the elongated element.
 59. The process as claimed in claim 57,wherein said shaped clearance engages the elongated element at a firstand a second mutually opposite base side, and a first and a secondheight side, each extending between said first and second base sides.60. The process as claimed in claim 46, wherein the elongated element isformed according to a substantially trapezoidal cross-section outlinefollowing the shaping step.
 61. The process as claimed in claim 46,wherein the shaping step comprises the step of forming at least onetab-shaped projection on the elongated element.
 62. The process as,claimed in claim 61, wherein said at least one tab-shaped projection hasa variable width depending on the volumetric flow rate of the continuousthread element close to the shaping rollers.
 63. The process as claimedin claim 46, wherein application of the elongated element onto theforming support takes place by at least one applicator memberoperatively supported relative to the shaping rollers and acting inthrust relationship toward the forming support.
 64. The process asclaimed in claim 46, wherein during applying of the elongated element,the forming support is driven in rotation and transversely moved by arobotized arm carrying the forming support.
 65. The process as claimedin claim 46, wherein the forming support is a toroidal support.
 66. Anapparatus for building tyres comprising: at least one forming support;and at least one assembly device to assemble components of elastomericmaterial on the forming support, said at least one assembly devicecomprising: at least one extruder to deliver a continuous thread elementof elastomeric material; at least one shaping device to shape thecontinuous thread element coming from the extruder, comprising at leastone pair of counter-rotating shaping rollers engaging the continuousthread element to form an elongated element having a predeterminedcross-section outline; and at least one applicator device to apply saidelongated element wound up into coils, onto the forming support, to saidat least one component of elastomeric material of the tyre; said atleast one shaping device further comprising: at least one device formonitoring at least one parameter indicative of the volumetric flow rateof the continuous thread element close to the shaping rollers; and atleast one adjusting device to adjust a feeding speed of the continuousthread element toward the shaping roller to keep the volumetric flowrate value within a predetermined range.
 67. The apparatus as claimed inclaim 66, wherein said extruder comprises at least one cylinderlongitudinally housing a rotating screw to urge the elastomeric materialalong the cylinder toward an outlet port of the extruder.
 68. Theapparatus as claimed in claim 67, further comprising at least onepositive-displacement pump operatively interposed between the rotatingscrew and the outlet port of the extruder.
 69. The apparatus as claimedin claim 68, wherein said positive-displacement pump is a gear pump. 70.The apparatus as claimed in claim 66, further comprising at least onestorage device for accumulation of the continuous thread element in astorage length between the extruder and the shaping rollers.
 71. Theapparatus as claimed in claim 70, further comprising at least onedriving device disposed downstream of the storage length to feed theshaping rollers with the continuous thread element.
 72. The apparatus asclaimed in claim 71, wherein said at least one driving device comprisesat least one pair of counter-rotating driving rollers.
 73. The apparatusas claimed in claim 66, wherein said at least one monitoring devicecomprises at least one detector for a cross-section area of thecontinuous thread element.
 74. The apparatus as claimed in claim 66,wherein said at least one monitoring device comprises at least onedetector for a width size of the elongated element.
 75. The apparatus asclaimed in claim 73, wherein said detector operates close to the shapingrollers.
 76. The apparatus as claimed in claim 66, wherein said at leastone adjusting device interacts with the extruder to modify deliveryspeed of the elastomeric material through the extruder.
 77. Theapparatus as claimed in claim 76, wherein said adjusting deviceinteracts with the extruder, thereby modifying a rotation speed of arotating screw, said rotating screw being part of the extruder.
 78. Theapparatus as claimed in claim 76, wherein said adjusting deviceinteracts with the extruder, thereby modifying a driving speed of apositive-displacement pump operatively disposed upstream of an outletport of the extruder.
 79. The apparatus as claimed in claim 71, whereinsaid at least one adjusting device interacts with said at least onedriving device to adjust the feeding speed of the continuous threadelement toward the shaping rollers.
 80. The apparatus as claimed inclaim 66, wherein said shaping rollers define a shaped clearance of aconformation corresponding to the cross-section outline of the elongatedelement.
 81. The apparatus as claimed in claim 80, wherein said shapedclearance engages the elongated element substantially over a wholeextension of a cross-section outline of the elongated element.
 82. Theapparatus as claimed in claim 80, wherein said shaped clearance has afirst and a second mutually opposite base side, and a first and a secondheight side, each extending between said first and second base sides.83. The apparatus as claimed in claim 80, wherein said shaped clearancehas a substantially trapezoidal outline.
 84. The apparatus as claimed inclaim 80, wherein said shaped clearance has at least one lateralinterspace to form at least one tab-shaped projection on the elongatedelement.
 85. The apparatus as claimed in claim 83, wherein said shapedclearance has at least one lateral interspace extending in the extensionof a major base side of said trapezoidal outline to form at least onetab-shaped projection on the elongated element.
 86. The apparatus asclaimed in claim 84, wherein said at least one lateral interspace givesthe shaped clearance a maximum width larger than a maximum permissiblewidth of the elongated element.
 87. The apparatus as claimed in claim80, wherein one of said shaping rollers is substantially cylindrical,said shaped clearance being defined by a circumferential groove formedin one of the shaping rollers.
 88. The apparatus as claimed in claim 66,wherein said at least one applicator device comprises at least oneapplicator member operatively supported relative to the shaping rollersand acting in thrust relationship toward the forming support.
 89. Theapparatus as claimed in claim 66, further comprising at least onerobotized arm carrying the forming support to drive the forming supportin rotation and move the forming support in a transverse directionduring application of the elongated element.
 90. The apparatus asclaimed in claim 66, wherein said forming support is a toroidal support.